Hosur_2011_Mol.Pharmacol_79_167

Despite evidence that smoking confers protection against neurological disorders, how and whether specific nicotinic receptor subtypes are involved is unknown. We reported previously that nicotine suppresses constitutive nuclear factor kappaB (NF-kappaB) activity and thereby proinflammatory cytokine (PIC) production in SHEP1 cells stably transfected with alpha4beta2 nicotinic receptors. Here, we report the anti-inflammatory effects of nicotine pretreatment in lipopolysaccharide (LPS)-stimulated SHEP1 cells. Nicotine (100-300 nM, concentrations found in smoker's blood) blocked LPS-induced NF-kappaB translocation and production of PICs interleukin (IL)-1beta and IL-6 but only partially blocked inhibitor of nuclear factor-kappaBalpha (IkappaBalpha) phosphorylation. These effects were exclusively in cells transfected with alpha4beta2 receptors but not in wild types. The cell-permeable calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester, the adenylate cyclase stimulant forskolin, and a specific protein kinase A (PKA) inhibitor PKI 14-22-amide failed to block the effect of nicotine on LPS-induced NF-kappaB translocation and IkappaBalpha phosphorylation. However, the effects of nicotine on NF-kappaB activity were significantly blocked by the highly specific janus kinase 2 (JAK2) inhibitor alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide (AG-490) and the signal transducer and activator of transcription 3 (STAT3) inhibitor 2-hydroxy-4-[[[[(4-methylphenyl)sulfonyl]oxy]acetyl]amino]-benzoic acid (NSC74859). These findings reveal a calcium- and cAMP-PKA-independent signaling cascade and suggest a role for JAK2-STAT3 transduction in alpha4beta2-mediated attenuation of LPS-induced inflammation. Anti-inflammatory effects of nicotine may therefore be mediated through alpha4beta2 receptors, the predominant high-affinity binding sites for nicotine in the central nervous system, in addition to the better-established alpha7 receptors.